Electric-field probes such as those used on electrostatically-floating sensor platforms, e.g. projectiles, typically are subject to electrical noise and signal drift. The electrical noise and signal drift usually are caused by a distributed charge as the charge accumulates and moves on such a projectile. For instance, a projectile in flight will charge due to triboelectrification or frictional contact with particles in the air. Combustion processes also can increase charge accumulation. These processes result in electrostatic charges attaching to the surface of the projectile while opposite charges are pulled away from the projectile by particles of a different material or by ions having different charge mobilities. As a conducting body accumulates charge, the charge redistributes itself according to Poisson's equation and the electrostatic boundary conditions; that is, according to the shape of the projectile. For example, triboelectrification may occur primarily on the nose, but some of the resultant charges will immediately move to the tail.
Charging is a cumulative process during flight and, at some point, the accumulated charge on the projectile becomes great enough that a counter-balancing discharging process begins. Areas typically experiencing higher charge density accumulation include those areas having high curvature and those at the extremities of the projectile. When the charge density becomes high enough, discharging begins. For example, discharging through corona can occur. These charging and discharging processes do not occur at all points over the surface of the projectile, but rather in particular areas. At some point, the average discharging current may equal the average charging current, and the total charge on the projectile may reach equilibrium. However, the instantaneous charging and discharging currents are rarely equal, even in equilibrium. In addition, an average current typically flows from the charging points to the discharging points, even in equilibrium. Unfortunately, the charging and discharging processes can generate significant amounts of electrical noise and can cause signal drift in an electric-field probe that is integrated into the projectile and used for electrostatic proximity detection.